A double template imprinted sorbent with chelating diamines was prepared by sol–gel process for the
selectiveseparationandenrichmentoftraceFe(III)fromnaturalwater samplesprior toitsdetermination
byflameatomicadsorptionspectroscopy(FAAS).TheresultingmaterialswerecharacterizedbySEM,FTIR,
elemental analysis andnitrogengas adsorption–desorption.ComparedwiththeCTABimprintedsorbent
(CTAB-imp)andtheFe(III)imprintedsorbent(Fe-imp),thedoubletemplateimprintedsorbent(Fe–CTABimp) had higher selectivity and adsorption capacity for Fe(III). In the presence of Cr(III) ion, selectivity
coefficient of the Fe–CTAB-imp for Fe(III) were 261 and 267, respectively, which are much higher than
that of CTAB-imp (1.61 and 1.32). The uptake capacities of the Fe–CTAB-imp were much higher than
those of sorbents prepared without CTAB template. The relative selectivity coefficient of the Fe–CTABimp for Fe(III)/Cr(III) was 68.9 times greater than the Fe-imp. The sorption isotherms on the Fe–CTABimp conformed to the Langmuir equation, and the theoretical sorption capacity was 36.90±3.16mg/g.
Furthermore, the Fe–CTAB-imp possessed fast sorption kinetics for Fe(III) from aqueous solution with
a saturation time of less than 5min, and could be used repeatedly. Combined with FAAS, the method
detection limitfor Fe(III) could reach the level of 0.26ng/mL. This sorbent has been successfully applied
tothe separationanddeterminationoftrace Fe(III)inreferencematerials, artificial seawater,freshwater
and nearshore seawater samples with satisfactory results.